The importance of phosphorus and potassium as fertilizers is widely known, and for this reason such compounds are widely use. However, so far it is not known any formulation containing, in a single product, the important combination of these two elements, both soluble in a weak acid like citric acid, and an important balance of other components like silica, quicklime, magnesia and micronutrients as complementary elements.
There are various papers dealing with attempts to obtain potassium from alkaline rocks by calcinations or by melting, and none of them uses or mentions the presence of phosphorus in the final fertilizer.
Brazil is an agronomical strong country, and for the success of productivity of the agricultural activities, a large amount of chemical fertilizers based on nitrogen, phosphorus and potassium (NPK) is usually employed in order to meet the demand from the plants and grass cultivated. Traditionally, the component that provides the required amount of potassium in NPK fertilizers is potassium chloride (KCl), whereas the components used for phosphorus are superphosphates, triple phosphates, and others, besides molten Yoorin thermophosphate, a phosphate of calcium and magnesium that is soluble in citric acid.
However, the use of potassium chloride salt has a number of drawbacks, among which the following are cited:
a) after application of the manure, if it rains much and if the rain is heavy, the potassium chloride will be rapidly solubilized and washed away down the declivities of the ground, probably into rivers, thus losing the function of fertilizing and carrying soluble salts into rivers and springs;
b) if, on the other hand, it does not rain after application of the manure, the potassium chloride may kill the plant that was to be fertilized by it, through a phenomenon called “saline effect”;
c) also, the chlorine ion present in potassium chloride, imparts taste to the leaves and fruits grown in the soil where this type of fertilizer has been used. The taste of coffee (fine cup) and tobacco is highly damaged, for which reason potassium chloride is replaced in these crops by potassium sulfate and/or potassium sulfate and magnesium, which are much rarer;
d) today, Brazil imports more than 90% of all potassium chloride used in agriculture, this percentage having the tendency to increase due to the increase in productivity of the cultivation of sugar cane and soybeans, and the rising need to meet the growing demand of food, which, as a result, represents the use of larger amounts of fertilizers.
In recent years, scholars have discussed the importance of manures from natural origin when made available in the soil, and at the same time they point out the harms caused by using chemical fertilizers indiscriminately. These studies also show relatively new facts, such as the verification of the importance of the presence of amorphous silica and of micronutrients available in the soil, which are released gradually in the presence of microorganism that exist naturally in the soil or are intentionally added, without the harms of chemical fertilizers. Some of these studies are pointed out hereinafter in order to illustrate the subject in discussion.
Trygon Agricultural Solutions mentions the wisdom and experience acquired by numberless farmers involved in different cultivations in the sense that, even using the best agricultural techniques, saw their productivities gradually decreasing, while the request for fertilizers increased. Modern agriculture has ignored the presence of silicon in the soils. Approximately each ton of soil contains about 277 kg of silicon, that is, any type of plant that grows in the soil is in contact with the huge amounts of silicon compounds, and even so the experts in agriculture do not regard silicon as being an essential element. Modern agriculture considers silicon not to be essential since about the mid-1800's, when artificial silicon was introduced. In 1980, one considered carbon, hydrogen, oxygen, nitrogen, phosphorus, sulfur, potassium, calcium, magnesium and iron to be essential nutrients. Between 1922 and 1954, manganese, copper, zinc, molybdenum, boron and chlorine were added thereto, thus totalizing 16 essential elements required for the growth of the plant. Many years passed until the last-named essential element, namely boron, was also considered. Plant physiologists are actively engaged in determining which other elements could be added to the list of the sixteen elements mentioned above and that are considered essential for the plants. In 1964, nickel, for example, was suggested as a candidate. Today, there are over 20 elements that are considered to be beneficial to the plants, but silicon continues to be included in this list.
It was found that silicon promotes absorption of other nutrients such as nitrogen, phosphorus, potassium, calcium, magnesium and zinc, among others. Several studies have demonstrated that silicon has significant influence on the accumulative growth of plants such as sugar cane, barley, wheat and rye. The cultivation of soybeans shows a marked decrease ion the growth in the absence of silicon. High concentrations of silicon at the borders of the plant tissues increase their resistance to attack by fungi and other organisms, and silicon also raises the resistance of the plant to saline effects, besides reducing the effect of toxicity caused by elements like aluminum, iron, manganese and other heavy metals.
In order for silicon to be made available for the plant, it has to be in the amorphous state or has to be present as a result of the chemical action exerted by organic matter, microbes, acids and enzymes encountered in the soil, as well as clays, which transform silica present in fine fractions into silicic acid, which can be absorbed by the plant. The transformation reaction is as follows:Organic matter+Microbes+Acids and Enzymes+Fine Fractions of Rocks containing silica and Clays=Silicic Acid.
M. J. Hodwon and A. F. Sangster, Silicon and Abiotic Stress, Oxford Brookes University, UK, Glendon College, York University, Canada, have found that there is considerable evidence that silicon is beneficial to plant growth, being added, today, as a fertilizer. Reductions in growth and in productivity have been frequently reported when silicon is supplied in smaller amounts than those considered optimum for determined plant culture. The deficiency of silicon in the soil may also entail quite complex effects on other nutrients. For instance, the improvement in the growth of cucumbers by the action of silicon depends on the unbalance in the supply of phosphorus and zinc. There is also a considerable number of works published regarding the effects of silicon on mineral toxicity. Silicon may have a beneficial effect on plant growth in saline conditions, it seems that silicon restricts the absorption of sodium for sensitive plant growth and that this mechanism blocks the perspiration passage flow. Studies made by W. J. Host and H. Mrchner, from Germany, show clearly the importance of silicon in blocking the toxicity caused by manganese. Various other studies have demonstrated the importance of silicon in preventing the toxicity caused by heavy metals. The toxicity caused by aluminum is also reduced or eliminated by the presence of silicon.
Patent application PI 080373-2 describes a process for preparing a potassium fertilizer, that is vitreous, totally soluble and exhibits high fertilization power due to the high solubility of potassium, as well as of other nutrients in the soil. The process for producing fertilizer described in that document comprises the steps of (a) preparing a mixture containing from 40 to 80% by weight of powdered alkaline rocks and from 20 to 60% by weight of powdered calcareous rocks, (b) melting the thus obtained mixture, (c) quenching the molten material and (d) grinding the resulting material.
Superphosphates and triple phosphates are also used as fertilizers, but their use contributes to excessive acidification of the soil, requiring growing amounts of ground calcareous rocks used in an additional operation called liming. The neutralization power of superphosphates and triple phosphates is zero. In the case of Yoorin thermophosphate, this phenomenon does not occur because it is derived from melting and has a neutralization power higher than 60% as compared with calcareous rocks (=100%).
Therefore, it is an objective of the present invention to provide a fertilizer that enables improved release of both phosphorus and potassium, in addition to the benefits of the presence of amorphous silica available and micronutrients, while exhibiting a nature of acidic neutralization of the soil.
Abreu, C. A., from the Instituto Agronômico de Campinas, in October 2006, studied the bleaching of potassium applied to the soil in the form of potassium chloride and of molten potassium thermophosphate, and concluded that the molten potassium thermophosphate provided lower losses of potassium in the soil, higher availability of this element and higher concentration of calcium, magnesium and phosphorus.
As a result, it is another objective of the present invention to make alternative fertilizers available in an economical manner, which enable improved release of phosphorus and potassium in the soil.